Qingliu Wu

Bio: Qingliu Wu is an academic researcher from Western Michigan University. The author has contributed to research in topics: Lithium & Materials science. The author has an hindex of 23, co-authored 42 publications receiving 2965 citations. Previous affiliations of Qingliu Wu include University of Kentucky & Oak Ridge National Laboratory.

Silicon-based Nanomaterials for Lithium-Ion Batteries - A Review

Abstract: There are growing concerns over the environmental, climate, and health impacts caused by using non-renewable fossil fuels. The utilization of green energy, including solar and wind power, is believed to be one of the most promising alternatives to support more sustainable economic growth. In this regard, lithium-ion batteries (LIBs) can play a critically important role. To further increase the energy and power densities of LIBs, silicon anodes have been intensively explored due to their high capacity, low operation potential, environmental friendliness, and high abundance. The main challenges for the practical implementation of silicon anodes, however, are the huge volume variation during lithiation and delithiation processes and the unstable solid-electrolyte interphase (SEI) films. Recently, significant breakthroughs have been achieved utilizing advanced nanotechnologies in terms of increasing cycle life and enhancing charging rate performance due partially to the excellent mechanical properties of nanomaterials, high surface area, and fast lithium and electron transportation. Here, the most recent advance in the applications of 0D (nanoparticles), 1D (nanowires and nanotubes), and 2D (thin film) silicon nanomaterials in LIBs are summarized. The synthetic routes and electrochemical performance of these Si nanomaterials, and the underlying reaction mechanisms are systematically described.

Optimizing areal capacities through understanding the limitations of lithium-ion electrodes

Abstract: Increasing the areal capacity or electrode thickness in lithium ion batteries is one possible means to increase pack level energy density while simultaneously lowering cost. The physics that limit use of high areal capacity as a function of battery power to energy ratio are poorly understood and thus most currently produced automotive lithium ion cells utilize modest loadings to ensure long life over the vehicle battery operation. Here we show electrolyte transport limits the utilization of the positive electrode at critical C-rates during discharge; whereas, a combination of electrolyte transport and polarization lead to lithium plating in the graphite electrode during charge. Experimental measurements are compared with theoretical predictions based on concentrated solution and porous electrode theories. An analytical expression is derived to provide design criteria for long lived operation based on the physical properties of the electrode and electrolyte. Finally, a guideline is proposed that graphite cells should avoid charge current densities near or above 4 mA/cm2 unless additional precautions have been made to avoid deleterious side reaction.

Advanced titania nanostructures and composites for lithium ion battery

Abstract: Owing to the increasing demand of energy and shifting to the renewable energy resources, lithium ion batteries (LIBs) have been considered as the most promising alternative and green technology for energy storage applied in hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and other electric utilities. Owing to its environmental benignity, availability, and stable structure, titanium dioxide (TiO2) is one of the most attractive anode materials of LIBs with high capability, long cycling life, high safety, and low cost. However, the poor electrical conductivity and low diffusion coefficient of Li-ions in TiO2 hamper the advancement of TiO2 as anode materials of LIBs. Therefore, intensive research study has been focused on designing the nanostructures of TiO2 and its composites to reduce the diffusion length of Li-ion insertion/extraction and improve the electrical conductivity of the electrode materials. In this article, the development of TiO2 and its composites in nano-scales including fabrication, characterization of TiO2 nanomaterials, TiO2/carbon composite, and TiO2/metal oxide composites to improve their properties (capacity, cycling performance, and energy density) for LIBs are reviewed. Meanwhile, the mechanisms for influences of the structure, surface morphology, and additives to TiO2 composites on the related properties of TiO2 and TiO2 composites to LIBs are discussed. The new directions of research on this field are proposed.

Aligned TiO2 Nanotube Arrays As Durable Lithium-Ion Battery Negative Electrodes

Abstract: Vertically aligned amorphous titania (TiO2) nanotubes are produced by anodizing Ti foils at various applied potentials in a neutral electrolyte solution containing fluoride ions. Pore size and wall thickness are tuned in the range from 30 to 70 nm and 17 to 35 nm, respectively, by adjusting the applied potential, in addition to tuning the tube length from 355 to 550 nm. Utilizing all of these films as negative electrode materials in lithium-ion batteries delivers stable capacities of 130–230 mAh g–1 and 520–880 mAh cm–3 up to 200 cycles. Microstructural analysis shows that there is no structural change or mechanical degradation in the active material, and the amorphous active material maintains good contact with the substrate/current collector. A continuum elasticity model for the tubular geometry is presented to understand the diffusion-induced stresses, fracture tendency, and stability in TiO2 nanotubes. Modeling results indicate that the fracture tendencies of nanotubes with the dimensions in this work...

Mechanical Alloying And Milling

Abstract: Mechanical alloying (MA) is a solid-state powder processng technique involving repeated welding, fracturing, and rewelding of powder particles in a high-energy ball mill. Originally developed to produce oxide-dispersion strengthened (ODS) nickel- and iron-base superalloys for applications in the aerospace industry, MA has now been shown to be capable of synthesizing a variety of equilibrium and non-equilibrium alloy phases starting from blended elemental or prealloyed powders. The non-equilibrium phases synthesized include supersaturated solid solutions, metastable crystalline and quasicrystalline phases, nanostructures, and amorphous alloys. Recent advances in these areas and also on disordering of ordered intermetallics and mechanochemical synthesis of materials have been critically reviewed after discussing the process and process variables involved in MA. The often vexing problem of powder contamination has been analyzed and methods have been suggested to avoid/minimize it. The present understanding of the modeling of the MA process has also been discussed. The present and potential applications of MA are described. Wherever possible, comparisons have been made on the product phases obtained by MA with those of rapid solidification processing, another non-equilibrium processing technique.

Performance and cost of materials for lithium-based rechargeable automotive batteries

Abstract: It is widely accepted that for electric vehicles to be accepted by consumers and to achieve wide market penetration, ranges of at least 500 km at an affordable cost are required. Therefore, significant improvements to lithium-ion batteries (LIBs) in terms of energy density and cost along the battery value chain are required, while other key performance indicators, such as lifetime, safety, fast-charging ability and low-temperature performance, need to be enhanced or at least sustained. Here, we review advances and challenges in LIB materials for automotive applications, in particular with respect to cost and performance parameters. The production processes of anode and cathode materials are discussed, focusing on material abundance and cost. Advantages and challenges of different types of electrolyte for automotive batteries are examined. Finally, energy densities and costs of promising battery chemistries are critically evaluated along with an assessment of the potential to fulfil the ambitious targets of electric vehicle propulsion. Electrification is seen as the future of automotive industry, and deployment of electric vehicles largely depends on the development of rechargeable batteries. Here, the authors survey the state-of-the-art advances in active materials, electrolytes and cell chemistries for automotive batteries.

Silicon-based Nanomaterials for Lithium-Ion Batteries - A Review

Abstract: There are growing concerns over the environmental, climate, and health impacts caused by using non-renewable fossil fuels. The utilization of green energy, including solar and wind power, is believed to be one of the most promising alternatives to support more sustainable economic growth. In this regard, lithium-ion batteries (LIBs) can play a critically important role. To further increase the energy and power densities of LIBs, silicon anodes have been intensively explored due to their high capacity, low operation potential, environmental friendliness, and high abundance. The main challenges for the practical implementation of silicon anodes, however, are the huge volume variation during lithiation and delithiation processes and the unstable solid-electrolyte interphase (SEI) films. Recently, significant breakthroughs have been achieved utilizing advanced nanotechnologies in terms of increasing cycle life and enhancing charging rate performance due partially to the excellent mechanical properties of nanomaterials, high surface area, and fast lithium and electron transportation. Here, the most recent advance in the applications of 0D (nanoparticles), 1D (nanowires and nanotubes), and 2D (thin film) silicon nanomaterials in LIBs are summarized. The synthetic routes and electrochemical performance of these Si nanomaterials, and the underlying reaction mechanisms are systematically described.